The present invention relates to an amplifier circuit, an integrated circuit device, an electronic instrument, etc.
It is desirable that an amplifier circuit amplify an input signal over a wide input range between a high-potential-side power supply and a low-potential-side power supply. A rail-to-rail amplifier circuit is known as such an amplifier circuit. For example, FIG. 13 of JP-A-2008-306698 discloses a related-art rail-to-rail amplifier circuit.
A rail-to-rail amplifier circuit includes a P-type differential section that includes P-type transistors, and an N-type differential section that includes N-type transistors. It is desirable to operate the P-type differential section when the voltage level of the input signal is low, and operate the N-type differential section when the voltage level of the input signal is high, for example.
An offset voltage occurs in the amplifier circuit due to a difference in transistor characteristics or an asymmetrical circuit layout. Therefore, an offset adjustment that cancels the offset voltage is required.
However, it was found that the offset voltage of the amplifier circuit (operational amplifier) in a mode in which the P-type differential section operates may differ from the offset voltage of the amplifier circuit in a mode in which the N-type differential section operates. Therefore, an appropriate offset adjustment may not be implemented when switching the operation mode.